Tidally Modulated Glacial Seismicity at the Foundation Ice Stream, West Antarctica

We investigate the occurrence of repeating glacial seismicity near the grounding line of the Foundation Ice Stream and further upstream using continuous broadband seismic data collected by Polar Earth Observing Network (POLENET/A‐NET) stations from 2014 through 2019. Through manual identification and cross‐correlation analysis, 2,237 discrete icequakes (1.5 ≤ ${\le} $ ML ≤ ${\le} $ 2.6) are detected in two spatial clusters, one located at the grounding line of the Foundation Ice Stream (2,219 event detections) and a second located further upstream proximal to a subglacial ridge (18 event detections). Seismicity is predominantly concentrated in the Schmidt Hills, located adjacent to the grounding line of the Foundation Ice Stream, and shows clear ocean tide modulation. Seismic events primarily occur during spring tides, and, on a shorter timescale, concurrent with the rising tide preceding daily maximum high tide. The seismicity can be attributed to stick‐slip motion and fracturing that preferentially occur during rising tides. Seismicity located further upstream in the southern portion of the Foundation Ice Stream most likely reflects basal stick‐slip processes associated with the subglacial topographic high. Plain Language Summary The study of glacial processes at the grounding line, where the ice sheet transitions from sitting on bedrock to floating on the ocean, is important for better understanding the transfer of ice from Antarctica's interior to the ocean. Icequakes, which are like earthquakes but caused by the movement of ice instead of rock, can be used to investigate glacial processes at the grounding line. In this study, we detect 2,237 icequakes in the Foundation Ice Stream region of West Antarctica between 2014 and 2019. Of the 2,237 icequakes detected, 2,219 icequakes are located near the grounding line of the Foundation Ice Stream. The timing of icequake occurrence near the grounding line is driven by the ocean tides, with icequakes predominantly occurring during rising tides and spring tides. A seasonal shift in the time of day at which icequakes occur is observed, which can be attributed to the shift in the time of daily high tide throughout the year. In addition to the icequakes located near the grounding line, 18 icequakes are detected further upstream near a prominent subglacial ridge. Key Points 2,237 discrete icequakes are detected in the Foundation Ice Stream region from 2014 through 2019 Seismicity is predominantly concentrated adjac